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US7727749B2 - Stereoselective bioconversion of aliphatic dinitriles into cyano carboxylic acids - Google Patents

Stereoselective bioconversion of aliphatic dinitriles into cyano carboxylic acids Download PDF

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US7727749B2
US7727749B2 US10/599,899 US59989905A US7727749B2 US 7727749 B2 US7727749 B2 US 7727749B2 US 59989905 A US59989905 A US 59989905A US 7727749 B2 US7727749 B2 US 7727749B2
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cyano
succinonitrile
isobutyl
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nit
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US20070196905A1 (en
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Michael P. Burns
Justin K. Weaver
John Wing Wong
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Pfizer Inc
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P7/00—Preparation of oxygen-containing organic compounds
    • C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P13/00—Preparation of nitrogen-containing organic compounds
    • C12P13/002—Nitriles (-CN)
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P13/00—Preparation of nitrogen-containing organic compounds
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P13/00—Preparation of nitrogen-containing organic compounds
    • C12P13/001—Amines; Imines
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P41/00—Processes using enzymes or microorganisms to separate optical isomers from a racemic mixture
    • C12P41/006—Processes using enzymes or microorganisms to separate optical isomers from a racemic mixture by reactions involving C-N bonds, e.g. nitriles, amides, hydantoins, carbamates, lactames, transamination reactions, or keto group formation from racemic mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T436/00—Chemistry: analytical and immunological testing
    • Y10T436/20—Oxygen containing
    • Y10T436/200833—Carbonyl, ether, aldehyde or ketone containing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T436/00—Chemistry: analytical and immunological testing
    • Y10T436/20—Oxygen containing
    • Y10T436/207497—Molecular oxygen

Definitions

  • the present invention is directed to novel biocatalytic processes for the regio- and stereoselective conversion of selected aliphatic dinitriles into corresponding cyanocarboxylic acids. More particularly, the present invention provides methods for the conversion of 2-isobutyl-succinonitrile into (S)-3-cyano-5-methylhexanoic acid, which is a useful intermediate in the synthesis of (S)-3-(aminomethyl)-5-methylhexanoic acid (pregabalin).
  • Pregabalin can be used for treating certain cerebral diseases, for example, in the treatment and prevention of seizure disorders, pain, and psychotic disorders. Since pregabalin is effective in improving cerebral functions, it is also useful in the treatment of geriatric patients.
  • the enzymatic hydrolysis of organic nitrites to corresponding carboxylic acids and amides provides an important alternative synthetic method to a broad spectrum of useful compounds.
  • Conventional chemical hydrolysis of nitrites to the corresponding carboxylic acids and amides is typically carried out using a strong acid or base catalyst at high reaction temperatures making it incompatible with compounds which contain sensitive functional groups.
  • the poor selectivity of chemical hydrolysis may result in unwanted by-products along with large quantities of inorganic salts.
  • enzymatic nitrile hydrolysis occurs under mild conditions (neutral pH, 30° C.) offering the potential for high chemo-, regio-, and stereoselectivity.
  • the formation of by-product inorganic salts is avoided.
  • nitrile-converting enzymes The best-known industrial applications of nitrile-converting enzymes are the production of acrylamide (T. Nagasawa et al., Tibtech., 1992, vol. 10, 402-408) and nicotinamide (T. Nagasawa et al., Appl. Environ. Microbiol., 1998, vol 54, 1766-1769), using a nitrile hydratase from Rhodococcus rhodochrous J1.
  • Several recent reviews (L. Martinková et al., Current Organic Chemistry, 2003, vol. 7, 1279-1295 and D. Cowan et al., Extremophiles, 1998, vol. 2, 207-216) describe the biochemistry and potential industrial applications of nitrile converting enzymes.
  • Enzymatic nitrile hydrolyses are catalyzed by nitrilases, which convert nitrites to the corresponding carboxylic acids, and nitrile hydratases, which convert nitrites to the corresponding amides.
  • Amidases, which hydrolyze amides to the corresponding carboxylic acids, can be used in combination with nitrile hydratases to convert nitrites to carboxylic acids.
  • nitrilase enzyme to prepare a carboxylic acid from the corresponding nitrile is disclosed in WO 02/072856. Incorporation of the enzyme into a polymer matrix with cross-linking provided a catalyst with improved physical and biochemical integrity.
  • K. Yamamoto, et al. J. Ferment Bioengineering, 1992, vol. 73, 125-129 describes the use of microbial cells having both nitrile hydratase and amidase activity to convert trans 1,4-dicyanocyclohexane to trans-4-cyanocyclohexanecarboxylic acid.
  • Stereoselective enzymatic conversions of nitriles have been described for the preparation of chiral carboxylic acids and amides enriched in one enantiomer (M Wieser et al., Chapter in Stereoselective Biocatalysis , Marcel Dekker Inc.: New York, 2000, 461-486).
  • a stereoselective nitrilase enzyme from Alcaligenes faecalis ATCC 8750 is used to prepare (R)-mandelic acid from racemic mandelonitrile (K. Yamamoto et al., Appl. Environ. Microbiol., 1991, vol. 57, 3028-3032).
  • a nitrilase from Rhodococcus rhodochrous NCIMB 11216 preferentially hydrolyzes (+)-2-methylhexanitrile in a racemic mixture of 2-methylhexanitrile leaving ( ⁇ )-2-methylhexanitrile unreacted (M. Gradley et al., Biotechnology Lett., 1994, vol. 16, 41-46).
  • U.S. Pat. No. 5,593,871 disclosed a process for preparing 2-alkanoic acid amides enriched in one enantiomer, from nitriles using microorganisms containing stereoselective nitrile hydratases.
  • Enantiopure ⁇ -amino acids and amides were prepared from racemic ⁇ -aryl and ⁇ -alkyl-substituted glycine nitriles using Rhodococcus sp. AJ270 containing a stereoselective nitrile hydratase and a stereoselective amidase (M.-C. Wang et al., J. Org. Chem., 2002, vol. 67, 6542). The foregoing references are hereby incorporated herein in their entirety.
  • racemic pregabalin particularly its efficacy as an anticonvulsant, has been found to be attributable primarily to the (S)-enantiomer.
  • regio- and stereoselective biocatalytic conversions of aliphatic dinitriles to cyanocarboxylic acids are achieved using enzyme catalysts having nitrilase activity.
  • the present invention relates to a novel method for preparing an (S)-enantiomer of a compound of formula I:
  • C3 has an (S) configuration
  • R 1 is hydrogen, (C 1 -C 6 ) alkyl or phenyl
  • R 2 is (C 1 -C 8 ) alkyl, (C 2 -C 8 ) alkenyl, (C 3 -C 8 ) cycloalkyl, —O(C 1 -C 6 ) alkyl, —CH 2 —CH 2 —O— (C 1 -C 6 )alkyl, (C 1 -C 6 )alkyl-OH, -phenyl-(C 1 -C 6 )alkyl-OH, -phenyl-O—(C 1 -C 6 )alkyl, phenyl or substituted phenyl;
  • R 1 is hydrogen, (C 1 -C 6 ) alkyl or phenyl;
  • Compounds of formula I are useful in synthesizing compounds having pharmaceutical activity, such as pregabalin.
  • R 1 and R 2 are independently hydrogen or C 1 to C 3 alkyl.
  • the compound of formula II is a racemic mixture comprising 3R and 3S isomers.
  • a preferred embodiment of the present invention is the process whereby racemic 2-isobutyl-succinonitrile (the compound of formula II wherein R 1 is H and R 2 is methyl) is converted into (S)-3-cyano-5-methylhexanoic acid (the compound of formula I wherein R 1 is H and R 2 is methyl) comprising the steps of:
  • reaction medium is an aqueous medium.
  • the recovered and unchanged (R)-isomer of compound II is subsequently racemized by heating with a weak base in the presence of an organic solvent.
  • a preferred base is 1,8-diazabicyclo[5.4.0.]undec-7-ene and a preferred solvent is toluene.
  • the resulting racemate of II may be recycled into either of the above stated processes at step (1a) or (2a).
  • the enzyme catalyst is in the form of whole microbial cells, extracts of microbial cells, partially purified enzymes, purified enzymes or enzyme catalysts that are immobilized on a support.
  • the enzyme catalyst is a partially purified enzyme.
  • partially purified enzymes include, but are not limited to NIT-101, NIT-102, NIT-103 (BioCatalytics Inc., Pasadena, Calif.), and nitrilase from Arabidopsis thaliana (Jülich Fine Chemicals, Irishlich, Germany).
  • the nitrilase enzyme catalyst is immobilized on a support.
  • immobilized nitrilase enzyme catalysts include but are not limited to NIT-102 C2 (BioCatalytics Inc., Pasadena, Calif.), NIT-102 immobilized on Eupergit (Röhm GmbH & Co. KG, Darmstadt, Germany), and nitrilase from Arabidopsis thaliana immobilized on Eupergit.
  • the immobilized nitrilase enzyme catalyst is NIT-102 C2.
  • the reaction media is comprised of distilled water or buffered water.
  • the buffered water is buffered to a pH in the range of about 5.0 to about 10.0 and most preferably to a pH in the range of about 6.0 to about 8.0.
  • the present invention also relates to a process for the preparation of (S)-3-(aminomethyl)-5-methylhexanoic acid (pregabalin) comprising the steps of:
  • the acid salt has the formula
  • M is Na, K, Li, NH 4 , NH 2 R 6 R 7 ,
  • alkyl is a straight or branched group of from 1 to 8 carbon atoms including but not limited to methyl, ethyl, propyl, butyl, iso-butyl, and tert-butyl.
  • cycloalkyl as used herein includes moieties derived from cyclic hydrocarbons containing from three to seven ring carbon atoms, including cyclic hydrocarbon moieties substituted with straight or branched alkyl moieties.
  • alkoxy means “alkyl-O—”, wherein “alkyl” is defined as above.
  • alkenyl is intended to include hydrocarbon chains of either a straight or branched configuration comprising one or more carbon-carbon double bonds which may occur in any stable point along the chain, such as ethenyl and propenyl. Alkenyl groups typically will have 2 to about 12 carbon atoms, more typically 2 to about 8 carbon atoms.
  • racemate means an equimolar mixture of a pair of enantiomers.
  • a racemate is usually formed when synthesis results in the generation of a stereocenter.
  • racemic mixture means racemate.
  • enantiomers refers to compounds which at the molecular level are nonsuperposable with mirror images of each other. Enantiomers may exist in either the (R) or (S) configuration.
  • stereoselective synthesis refers to a chemical reaction that leads to formation of a single stereoisomer or an enantiomer-enriched mixture of isomers from among two or more possible stereoisomers.
  • regioselective refers to a reaction that takes place at a single atom or group of atoms from among two or more possible atoms or groups of atoms.
  • the regioselective hydrolysis of a dinitrile results in the conversion of a single nitrile group to a carboxyl group.
  • enzyme catalyst means a catalyst which is characterized by either a nitrilase activity or a combination of a nitrile hydratase activity and an amidase activity.
  • the catalyst may be in the form of a whole microbial cell, permeabilized microbial cell(s), one or more cell component of a microbial cell extract, partially purified enzyme(s), or purified enzyme(s).
  • enantiomer excess refers to the mole fraction of the dominant enantiomer in a mixture of enantiomers expressed as a percentage.
  • aqueous reaction mixture means a mixture of the substrate and enzyme catalyst in a largely aqueous medium.
  • nitrilase activity means an enzyme activity that converts a nitrile group to a carboxylic acid group.
  • nitrile hydratase activity means an enzyme activity that converts a nitrile group to an amide group.
  • aminodase activity means an enzyme activity that converts an amide group to a carboxylic acid group.
  • ATCC is American Type Culture Collection located at 10801 University Boulevard, Manassas, Va., 20110-2209, U.S.A. BioCatalytics Inc. is located at 129 N. Hill Avenue, Suite 103, Pasadena, Calif., 91106, U.S.A. Jülich Fine Chemicals GmbH is located at Rudolf-Schulten-Stra ⁇ e 5, D-52428 Irishlich, Germany.
  • the present invention provides an enzymatic method for preparing aliphatic cyanocarboxylic acids of formula I from dinitriles of formula II. Any suitable method commonly used in the art may be used to prepare the dinitrile (II) starting materials.
  • Scheme 1 refers to a specific embodiment of the present invention wherein a chemo-enzymatic method is used in the conversion of 2-isobutyl-succinonitrile (V) into (S)-3-cyano-5-methylhexanoic acid (VI).
  • Compound VI may be used as an intermediate in the synthesis of pregabalin (VII) as illustrated in Scheme 2.
  • Step 3 of Scheme 1 depicts the racemization of by-product (R)-isomer (Va) and subsequent recycle into Step 2.
  • racemic 2-isobutyl-succinonitrile (V) is formed by the condensation of isovaleraldehyde (III) with ethylcyanoacetate (IV) followed by the addition of KCN.
  • the racemate arises from the stereocenter created at the C 3 carbon atom of V.
  • Step 2 of Scheme 1 depicts the regio- and stereoselective hydrolysis of the dinitrile V racemate yielding (S)-3-cyano-5-methylhexanoic acid (VI) plus unchanged (R)-isomer of V.
  • the nitrilase catalyzed hydrolysis of 2-isobutyl-succinonitrile (V) into (S)-3-cyano-5-methylhexanoic acid VI is both regioselective and stereoselective.
  • Regioselectivity is based upon conversion of the cyano group into a carboxyl group at the C1 carbon atom only.
  • the reaction is stereoselective in that the (S) enantiomer of V is predominantly involved in the conversion leaving the (R)-enantiomer essentially unchanged.
  • an acid salt VIa of S-cyanoacid VI is hydrogenated in a subsequent step to obtain (S)-3-(aminomethyl)-5-methylhexanoic acid (pregabalin).
  • the reaction is carried out in the presence of a hydrogenation catalyst, preferably Raney nickel.
  • Acceptable acid salts include compounds of formula VIa wherein M is Na, K, Li, NH 4 , NH 2 R 6 R 7 , NH 3 R 6 or NH(R 6 ) 2 R 7 wherein R 6 and R 7 are independently (C 1 -C 6 )alkyl.
  • Another objective of the current invention is to avoid economic waste by recycling or reusing the unchanged (R)-dinitrile Va.
  • the present invention therefore, provides a method for the racemization of the (R)-dinitrile (Step 3, Scheme 1) and subsequent recycle through Step 2 of Scheme 1.
  • nitrilase activity having nitrilase activity or a combination of nitrile hydratase and amidase activities
  • screening protocols such as enrichment isolation techniques, which initially select microorganisms based on their ability to grow in media containing the enriched nitrile.
  • Enrichment isolation techniques typically involve the use of carbon-limited or nitrogen-limited media supplemented with an enrichment nitrile, which can be the nitrile substrate for the desired bioconversion, or a structurally similar nitrile compound.
  • Microorganisms that possess nitrilase activity can be initially selected based on their ability to grow in media containing the enrichment nitrile. Gavagan et al., ( Appl. Microbiol.
  • Biotechnol . (1999) vol. 52, 654-659) used enrichment techniques to isolate a Gram-negative bacterium, Acidovorax facilis 72W (ATCC 55746), from soil, using 2-ethylsuccinonitrile as the sole nitrogen source. Acidovorax facilis 72W (ATCC 55746) was shown to be useful for the selective conversion of 2-methylglutaronitrile to 4-cyanopentanoic acid. Enrichment techniques were also used to isolate the thermophilic bacterium, Bacillus pallidus Dac521, which catalyzes the conversion of 3-cyanopyridine to nicotinic acid (Almatawah and Cowan, Enzyme Microb. Technol . (1999) vol.
  • Microorganisms isolated by enrichment techniques can be tested for nitrile hydrolysis activity by contacting suspensions of microbial cells with a nitrile compound and testing for the presence of the corresponding carboxylic acid using analytical methods such as high performance liquid chromatography, gas liquid chromatography, or liquid chromatography mass spectrometry (LCMS).
  • analytical methods such as high performance liquid chromatography, gas liquid chromatography, or liquid chromatography mass spectrometry (LCMS).
  • enzyme engineering can be employed to improve various aspects of the enzyme(s). These improvements can be useful for the present invention and include increasing selectivity, catalytic efficiency of the enzyme, stability to higher temperatures and a wider range of pH, and enabling the enzyme to operate in a reaction medium including a mixture of aqueous buffer and organic solvent.
  • a variety of techniques, which can be employed in the present invention, to produce an enzyme catalyst having nitrilase activity or nitrile hydratase and amidase activities in addition to having an improved yield, throughput, and product quality suitable for a particular bioconversion process include but are not limited to enzyme engineering techniques such as rational design methods which include site-directed mutagenesis, and directed evolution techniques utilizing random mutagenesis or DNA shuffling techniques.
  • Suitable enzyme catalysts for the conversion of compounds of formula II into compounds of formula I are in the form of whole microbial cells, permeabilized microbial cells, extracts of microbial cells, partially purified enzymes or purified enzymes, and such catalysts can be immobilized on a support.
  • This process can be carried out in a single phase by contacting 2-isobutyl-succinonitrile with an enzyme catalyst in distilled water, or in an aqueous solution of a buffer, which will maintain the initial pH of the reaction between 5.0 and 10.0, preferably between 6.0 and 8.0.
  • Suitable buffering agents include potassium phosphate and calcium acetate.
  • the pH of the reaction mixture may change due to the formation of an ammonium salt of the carboxylic acid from the corresponding nitrile functionality of the dinitrile.
  • the reaction can be run with no pH control, or a suitable acid or base can be added over the course of the reaction to maintain the desired pH.
  • enzyme catalysts using technologies such as enzyme engineering and directed evolution, which will operate effectively over wider pH ranges.
  • reaction mixtures comprised of two phases: an aqueous phase, which initially contains enzyme and dissolved 2-isobutyl-succinonitrile, and an organic phase, which consist mainly of racemic 2-isobutyl-succinonitrile.
  • Two-phase reaction mixtures are prepared by adding 2-isobutyl-succinonitrile to an aqueous solution of enzyme and buffer agents such that the amount of 2-isobutyl-succinonitrile added exceeds it aqueous solubility limit.
  • the aqueous solubility limit of 2-isobutyl-succinonitrile in 50 mM potassium phosphate (30° C., pH 7.5) is approximately 0.06M.
  • reaction mixtures comprised of three phases: an aqueous phase, which initially contains dissolved 2-isobutyl-succinonitrile, an organic phase, which consists mainly of racemic 2-isobutyl-succinonitrile, and a solid phase, which consists of enzyme immobilized on an insoluble support.
  • aqueous phase which initially contains dissolved 2-isobutyl-succinonitrile
  • organic phase which consists mainly of racemic 2-isobutyl-succinonitrile
  • solid phase which consists of enzyme immobilized on an insoluble support.
  • Three-phase reaction mixtures are prepared by the procedure described for two-phase reaction mixture except that an enzyme immobilized on an insoluble support is used in place of an un-immobilized enzyme.
  • the enzyme may be immobilized in a polymer matrix or an insoluble support.
  • Immobilized enzyme catalysts can be used repeatedly and in continuous processes, and can be separated from the products of the enzymatic process more easily than un-immobilized enzyme catalysts.
  • Methods for the immobilization of enzymes in a polymer matrix, such as calcium alginate or polyacrylamide, or an insoluble support, such as celite, are well known to those skilled-in-the-art.
  • NIT-102 C2 BioCatalytics Inc., Pasadena, Calif.
  • which is a nitrilase enzyme immobilized on an insoluble support is particularly useful for the conversion of II to III, since it can be used repeatedly in batch or continuous processes.
  • NIT-102 C2 used in a reaction is chosen to obtain a desired reaction rate and depends on the specific activity of the catalyst and the concentration of substrate. Typically, NIT-102 C2 is used in the range of about 0.001 g to 0.3 g moist weight per mL of reaction volume, with a preferred range of 0.01 to 0.15 g moist weight per mL of reaction volume.
  • NIT-101 lyophilized lysates prepared from microbial cells and designated as NIT-101, NIT-102, NIT-103 (BioCatalytics Inc., Pasadena, Calif.), and nitrilase from Arabidopsis thaliana (Jülich Fine Chemicals, Irishlich, Germany) are also useful for the conversion of II to III.
  • NIT-101, NIT-102, NIT-103 and A. thaliana nitrilase with I in an aqueous reaction mixture results in the formation of II.
  • Reactions using NIT-101, NIT-102, NIT-103 and nitrilase from Arabidopsis thaliana can be carried out in two-phase reaction mixtures using catalyst concentrations ranging from 0.001-0.04 g dry weight per ml reaction volume, with a preferred range of 0.002-0.02 g dry weight per mL reaction volume.
  • the temperature of the hydrolysis reaction is chosen to both optimize the reaction rate and the stability of the enzyme catalyst activity.
  • the temperature of the reaction may range from just above the freezing point of the suspension (ca. 0° C.) to 60° C., with a preferred range of reaction temperature from 5° C. to 35° C.
  • Recovery of the (3S) isomer of the compound of formula I and recovery of unchanged (3R) isomer of the compound of formula II may be carried out using suitable separation, isolation and purification techniques well-known to those skilled in the art.
  • the unchanged (3R) isomer of the compound of formula II is separated from the basic aqueous reaction mixture by extraction with an organic solvent such as ethyl acetate.
  • the acid salt of the (3S) isomer of the compound of formula I is preferentially dissolved in the aqueous layer and is subsequently isolated by acidification and extraction with an organic solvent such as ethyl acetate.
  • the compounds of formula I can be used to synthesize compounds, such as pregabalin, having usefulness in the treatment of such disorders as epilepsy, convulsion, anxiety, pain, and neurodegenerative disorders, including Alzeimer's disease, Huntington's disease and Parkinson's disease.
  • a 125 mL jacketed reaction vessel maintained at 30° C. was charged with 2-isobutyl-succinonitrile (3.33 g), NIT-102 (0.5 g) and 122 mL of 50 mM potassium phosphate buffer (pH 7.5) containing 5 mM DTT and 1 mM EDTA (reaction buffer). After stirring for 12.5 h, the product mixture was extracted with ethyl acetate (4 ⁇ 50 mL). The ethyl acetate extracts were removed, and the aqueous part was adjusted to pH 2.5 with 4M HCl and extracted with ethyl acetate (3 ⁇ 50 mL).
  • reaction vessel Two 125 mL jacketed reaction vessels maintained at 30° C. were each charged with 2-isobutyl-succinonitrile (6.81 g), NIT-102 C2 (1.70 g) and 118.2 mL of reaction buffer. After stirring for 24 h, the product mixtures were decanted, leaving the enzyme catalyst in the reaction vessels. Reaction buffer (20 mL) was added to the each reaction vessel, stirred for approximately 2 min., and then decanted and added to the product mixtures. Reactions were repeated by adding 2-isobutyl-succinonitrile (6.81 g) and reaction buffer (118.2 mL) to each reaction vessel and stirring the reaction mixtures for 24 h.
  • Methyl (S)-3-cyano-5-methylhexanoate was prepared from potassium (S)-3-cyano-5-methylhexanoate and analyzed by chiral GC to reveal an enantiomeric purity of 99.1% e.e.
  • a 125 mL jacketed reaction vessel maintained at 30° C. was charged with 2-isobutyl-succinonitrile (6.53 g), NIT-102 C2 (2.61 g), 120 g of reaction buffer, and purged with nitrogen.
  • the resulting mixture was stirred for 24 h and then decanted to a 250 mL glass bottle, leaving the catalyst in the reaction vessel.
  • the reaction was repeated by recharging the reaction vessel containing the used catalyst with 2-isobutyl-succinonitrile (6.53 g) and 120 g of reaction buffer, purging with nitrogen, and stirring the resulting mixture for 24 h.
  • Reaction samples (0.1 mL) were mixed with 0.4 mL of water:methanol:trifluoroacetic acid (60:40:0.09, v/v/v) and analyzed by HPLC on a SymmetryTM C8 column (150 ⁇ 3.9 mm) maintained at 30° C. The column was eluted with water:methanol:trifluoroacetic acid (60:40:0.09, v/v/v) and detection was carried out with a refractive index detector.

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